Sock and process for the production thereof

ABSTRACT

An ankle length sock having an opening welt positioned in the vicinity of an ankle of a wearer, and having an elastic welt provided at the opening welt is provided. The sock may include a compression area with high elasticity and high compressive force disposed laterally in a diagonal direction in an area extending from behind an arch portion to an Achilles tendon portion above a heel portion. A size control course with a knitted fabric increased by 4-20 courses may be disposed between the compression area and the heel portion. An additional pocket may be interknit with 2-24 courses by reverse knitting, repeatedly alternating normal rotation and reverse rotation of the circular knitting machine cylinder, at a position on the sole portion side between the size control course and the compression area.

RELATED APPLICATIONS

The present application claims priority to Japanese Patent Application Number 2008-053658 filed Mar. 4, 2008, the entirety of which is hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a sock and a process for the production thereof. It is an object of the present invention to prevent slipping of a heel side of an elastic welt disposed at an opening of a sock, particularly in an ankle-length sock.

BACKGROUND ART

When wearing sneakers or pumps, or when wearing athletic shoes such as tennis shoes, an ankle-length sock is used which has an opening welt positioned in the vicinity of the ankle of the wearer. In an ankle-length sock, the leg portion is short, and the leg portion and an elastic welt are hidden inside the shoe, or are only slightly visible when the shoe is worn, and this is desirable from the standpoint of fashion. It should be noted that in ankle-length socks, the position corresponding to the “leg portion” of an ordinary sock is typically short and is generally referred to as the “ankle portion,” and in this Specification as well, it is referred to as the “ankle portion.” A sock of a type in which the ankle portion and the elastic welt are completely hidden within the shoe is sometimes referred to as having a “ghost length” so as to distinguish it from other ankle-length socks, but in this Specification, both are referred to as having an “ankle length.”

During activities such as jogging, insufficient elasticity in the longitudinal direction or rubbing against the shoe can cause the heel side of the elastic welt of such an ankle-length sock to slip, resulting in discomfort while wearing it. There are broadly two types of causes of slipping of ankle-length socks: a structural factor illustrated in FIG. 6 and an external factor illustrated in FIG. 7. These factors are described as follows.

1) Structural Factor

As shown in FIG. 6( a), if a sock has an ankle-length structure, the sock as a whole fits the foot while it is motionless, and no slipping occurs. However, as shown in FIGS. 6( b) and (c), when the center of gravity is applied to the toes while walking, the knitted fabric at the periphery of the toes stretches, thereby increasing the surface area of the portion indicated by arrow 61. When this occurs, the elasticity of the sock is no longer able to accommodate the increased surface area of the portion indicated by arrow 61, so the heel side of the elastic welt slips in the direction of arrow 62, as shown in FIG. 6( d). The foregoing is the structural factor.

2) External Factor

As shown in FIG. 7( a), if a shoe is worn with an ankle-length sock, the sock as a whole fits the foot while it is motionless, and no slipping occurs. However, as shown in FIGS. 7( b) and (c), when the heel has risen upwards while walking, a force is generated which tends to return the shoe to its original position (the force in the direction of arrow 71), and a force is generated raising the heel upward (the force in the direction of arrow 72). These forces oppose each other, resulting in friction. Consequently, as shown in FIG. 7( d), the heel side of the elastic welt slips in the direction of arrow 73. The foregoing is the external factor.

A sock was previously disclosed to prevent slipping by providing a plurality of gore lines formed in trapezoidal knitted fabrics at the heel portion, so as to increase the size of the heel portion, as for example in Patent Reference 1. Patent Reference 2 discloses a sock with a compression area formed vertically along the periphery of the heel portion with the ankle as a base point.

-   -   Patent Reference 1: Japanese Laid-Open Patent Application No.         2001-164405     -   Patent Reference 2: Japanese Utility Model Registration No.         3117341

However, slipping of the heel side of the elastic welt of an ankle-length sock occurs due to increased surface area of the knitted fabric of the sole portion, as well as due to rubbing against the shoe. Thus, Patent Reference 1, in which the sock only has a structure in which the heel portion is knitted larger than usual, discloses a sock in which it is impossible to impart an upward force to resist the downward slipping of the heel side of the elastic welt, so the slip-preventing effect is insufficient.

Furthermore, since the ankle portion of an ankle-length sock is very short, providing a compression area in a structure such as that of Patent Reference 2 is difficult from the start. Moreover, even if the structure of Patent Reference 2 were applied to an ankle-length sock, it would not be possible to impart a force in a direction to resist the downward slipping of the heel side of the elastic welt, so no slip-preventing effect is obtained. Therefore, socks having the structures of Patent Reference 1 and Patent Reference 2 exhibit a retracting effect due to rubbing against the shoe as well as slipping, when the wearer is walking.

It should be noted that a sock which is knitted with a circular knitting machine has a ground yarn embedded in a helical configuration from the elastic welt to the toe portion while being inlaid with rubber yarns, so as to have elasticity in the course direction. When the rubber yarns are inlaid, the elastic force of the knitted fabric can be freely adjusted by changing the yarn feed volume.

However, such circular knitting machine technology only controls the elastic force in the course direction of the sock, making it difficult to raise the elastic force in a diagonal direction in a lateral area from behind the arch portion of the sock to the Achilles tendon portion above the heel portion.

The present invention was devised with the foregoing problems of the prior art in mind, and has as its object to provide a sock which is able to prevent slipping of a heel side of an elastic welt, even if it has an ankle length portion, and a process for the production thereof.

SUMMARY OF THE INVENTION

Socks are described below that may prevent slipping of a heel side of an elastic welt. The invention may include any of the following aspects in various combinations and may also include any other aspect described below in the written description or in the attached drawings.

In one embodiment, the sock is an ankle-length sock having an opening welt positioned in the vicinity of the ankle of the wearer and with an elastic welt provided in the opening welt, and characterized in having a compression area with high elasticity and high compressive force and disposed laterally in a diagonal direction in an area from behind the arch portion of the sock to the Achilles tendon portion above the heel portion. In one aspect, a size control course comprising a knitted fabric increased by 4-20 courses is disposed between the compression area and the heel portion.

In another aspect, an additional pocket may be interknit with 2-24 courses by reverse knitting at a position on the sole portion side between the size control course and the compression area. The reverse knitting may be performed by repeatedly alternating normal rotation and reverse rotation of the circular knitting machine cylinder. In yet another aspect, the compression area may provide a tensile retention force between about 4.5 Newtons and about 5.5 Newtons.

A process for producing a sock of the present invention may utilize a circular knitting machine. For one embodiment, the knitting process may be characterized by performing a desired course knitting of an elastic welt and an ankle portion by normal knitting with normal rotation of a circular knitting machine cylinder. A desired course knitting of the instep side of the toe portion may be performed through reverse knitting by repeatedly alternating normal rotation and reverse rotation of the circular knitting machine cylinder and decreasing the number of stitches. Subsequently, a desired course knitting of a sole side of the toe portion may be performed by reverse knitting and increasing the number of stitches, and elastic yarns may be inlaid while knitting ground yarns when performing the desired course knitting of the compression area through normal knitting.

The compression area may be knitted using course knitting and the additional pocket may be reverse knitted with 2-24 courses. In another aspect, the size control course may be knit with 4-20 courses using normal knitting and a heel portion may be knitted using reverse knitting with a half needles on the opposite side from the half needle of the cylinder used when knitting the additional pocket. The opening may then be seamed upon completion of knitting such that the seamed opening is positioned on the sole side of the heel portion.

In accordance with the present invention, in addition to the fact that the elastic welt is secured around the ankle, in particular, there is provided a compression area with high elasticity and high compressive force that is disposed laterally in a diagonal direction, in an area from behind the arch portion to the Achilles tendon portion above the heel portion, so that force is imparted in a direction to resist the downward slipping of the heel side of the elastic welt, thereby making it possible to prevent slipping of the elastic welt of the ankle-length sock.

As shown in FIG. 5, if the structure of the present invention is employed, when the toes are extended during walking, a lifting force can be generated in the upward direction of FIG. 5 (the direction of arrows 52 and 53) by the compression area and the elastic welt, so as to provide resistance against the slipping direction of the heel portion (the direction of arrow 51). Therefore, in the sock of the present invention, when the toes are extended while walking, the expanding shape of the heel of the wearer is utilized to enable the formation of a state in which the sock hangs on the heel, thereby reducing the range within which the knitted fabric of the sole stretches and retracts into the shoe (the range of arrow 54), thereby making it possible to solve the problem of slipping while walking.

The foregoing paragraphs have been provided by way of general introduction, and are not intended to limit the scope of the following claims. The presently preferred embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing illustrating the sock of the present invention as viewed from the side.

FIG. 2 is a drawing illustrating the sock of the present invention as viewed from above.

FIG. 3 is a drawing illustrating the process for production of the sock of the present invention, showing the order of knitting the various parts.

FIG. 4 is a drawing illustrating the process for production of the sock of the present invention, showing a development diagram of the sock.

FIG. 5 is a drawing illustrating the advantageous effects of the sock of the present invention.

FIG. 6 is a drawing illustrating the structural factors which are among the causes for slipping of a prior art ankle-length sock.

FIG. 7 is a drawing illustrating the external factors which are among the causes for slipping of a prior art ankle-length sock.

FIG. 8 is a drawing illustrating a test method for measuring slipping, in the case where the holding clipper of a digital force gauge is attached at the heel side of the elastic welt.

FIG. 9 is a drawing illustrating a test method for measuring slipping, in the case where the holding clipper of a digital force gauge is attached at the center of the arch portion.

FIG. 10 is a drawing illustrating a test method for measuring slipping, in the case where the holding clipper of a digital force gauge is attached at the outer side of the sole portion near the heel.

FIG. 11 is a drawing illustrating a test method for measuring slipping, in the case where the holding clipper of a digital force gauge is attached at the inner side of the sole portion near the heel.

PREFERRED EMBODIMENTS

In the sock of the present invention, if a size control course is provided with knitted fabric increased by 4-20 courses, particularly between the compression area and the heel portion, then the heel portion will be of a sufficient size to surround the entire heel of the wearer and fit so as to accommodate the entire heel, thereby enhancing the effect of preventing slipping of the elastic welt.

In the sock of the present invention, when an additional pocket is interknit with 2-24 courses at a position on the sole portion side between the size control course and the compression area by reverse knitting of repeatedly alternating between normal rotation and reverse rotation of the circular knitting machine cylinder, particularly, then the knitted fabric on the sole portion side is knitted with a greater knitting density to approximate the shape of a human heel, thereby making it possible to naturally fit the heel and further enhancing the effect of preventing slipping of the elastic welt.

According to careful investigations by the present inventors to determine conditions under which it is possible to favorably achieve a slip-preventing effect, as well as conditions under which there is no loss of comfort while wearing the sock, it was found to be preferable for the compression area of the sock of the present invention to provide a tensile retention force in a range of 4.5 N to 5.5 N.

Moreover, in the process for the production of the sock of the present invention, it is further preferable to perform a desired course knitting of the compression area, and subsequently to knit the additional pocket with 2-24 courses by reverse knitting, then to knit the size control course with 4-20 courses by normal knitting, and then to knit a heel portion by reverse knitting with needles of one half of the cylinder on the opposite side from the needles of the other half of the cylinder used when knitting the additional pocket, and then to seam the opening upon completion of knitting so that the seamed opening is positioned on the sole side of the heel portion.

The reasons why it is better to have an additional pocket and a size control course are as described above. Since socks knitted with a circular knitting machine have a knitted opening which is sewn together, a problem exists in that the sock loses its wearing comfort due to unevenness that develops in the sewn portion (known as a Rosso linking course). However, if the above-described process is used, the Rosso linking course can be formed at a position on the heel where the skin is thickest on the bottom of the human foot, so that the unevenness of the Rosso linking course is almost imperceptible, which is advantageous for comfort while wearing the sock.

When knitting a sock with a circular knitting machine, typically, the order of knitting is: the elastic welt, then the ankle portion, then the heel portion, then the foot body portion, and then the toe portion. However, a characteristic of the process of producing the sock of the present invention is that knitting is done in the following order: the elastic welt, then the ankle portion, then the toe portion, then the compression area, then the additional pocket, then the size control course, and then the heel portion.

In particular, the toe portion is knitted as a toe portion with a large surface area produced by reverse knitting, repeatedly alternating normal rotation and reverse rotation of the circular knitting machine cylinder, and by repeatedly raising and lowering a needle in half rotation knitting. An angle of initial and final knitted fabric of the toe portion is formed in a diagonal orientation, and behind that, a knitted compression area is formed in an area extending from behind the arch portion to the Achilles tendon portion above the heel portion. Accordingly, the sock is formed in a state such that it hangs at the position of the Achilles tendon, thereby preventing the ankle-length sock from slipping.

EXAMPLES

The sock of the present invention is now explained in further detail on the basis of examples. FIG. 1 is a drawing illustrating a sock of the present invention viewed from the side.

Sock S of this example is an ankle-length sock with a sock opening H and an opening welt K positioned in the vicinity of the ankle of the wearer. An elastic welt 1, which suitably tightens around the periphery of the ankle due to rubber yarns embedded in knitted ground yarns, is knitted into the opening welt K.

Reference Numeral 2 is an ankle portion, and in the ankle-length sock of this example, the vertical length thereof is extremely short.

The most characteristic feature of the present invention is that a compression area 7 with high elasticity and high compressive force is disposed in an area extending from behind an arch portion T to an Achilles tendon portion A above a heel portion 10 in a diagonal direction from the lower left to the upper right, when the sock S is viewed from the side, as shown in FIG. 1, with toe portions 3 and 6 on the left side of the drawing and the heel portion 10 on the right side of the drawing. Since the toe portions 3 and 6 are in the front, and the heel portion 10 is in the back, “behind an arch portion T” refers to a position more on the side of the heel 10 than the arch portion T.

“High elasticity and high compressive force” refers not only to the fact that the knitted fabric stretches well, but also signifies a high level of force in a direction which causes the knitted fabric to return to its original state. Here, the compressive force of the compression area 7 is relatively higher than that of other knitted portions of the sock, such as an ankle portion 2, the toe portions 3 and 6, an additional pocket 8, a size control course 9, and the heel portion 10. However, a structure may be employed wherein the compressive force is made identical to that of the elastic welt 1, by causing the volume of fed elastic yarns to be identical to that of the elastic welt 1, for example. Furthermore, the compressive force of the compression area 7 may be higher than the compressive force of the elastic welt 1, in order to significantly enhance the slip-preventing effect.

Several methods may be used to form the compression area 7 so that it has high elasticity and high compressive force. For example, there is the method of rubber knitting a knitted fabric, or the method of using yarns containing polyurethane in the back yarns, or the method of inlaying rubber yarns while embedding ground yarns. However, the most advantageous method is that of inlaying rubber yarns while embedding ground yarns, in order to impart continuous and direct compressive force in a diagonal direction in an area extending from behind the arch portion T to the Achilles tendon portion A above the heel portion 10.

In the sock S of this example, the size control course 9, having a knitted fabric increased by 8 courses, is provided between the compression area 7 and the heel portion 10. Consequently, the heel portion 10 becomes large enough to surround the entire heel of the wearer so as to readily fit the entire heel and no longer slip, thereby enhancing the slip-preventing effect on the heel side of the elastic welt 1.

The additional pocket 8 interknit with 6 courses, is provided at a position on the sole portion side between the size control course 9 and the compression area 7, by reverse knitting, repeatedly alternating normal rotation and reverse rotation of the circular knitting machine cylinder. Consequently, as shown in FIG. 1, the knitted fabric on the sole portion side is knitted with a greater knitting density to approximate the shape of a human heel, making it possible to most naturally fit the heel, thereby further enhancing the effect of preventing slipping of the elastic welt.

In addition, the sock S of this example exhibits an effect of absorbing impact to the heel during walking, since the inner surfaces of the heel portion 10, the size control course 9, and the additional pocket 8 are formed by pile knitting. Accordingly, the sock S of this example is suited for walking as well as jogging.

Reference Numeral 3 is the instep side of the toe portion, and Reference Numeral 6 is the sole side of the toe portion. The surface area (of toe portions 3 and 6) is increased by knitting a fabric while changing the number of knitting needles, and by repeatedly raising and lowering the needles during half rotation. An angle of initial and final knitted fabric of the toe portions 3 and 6 is formed in a diagonal direction, and behind that, a knitted compression area 7 is formed in an area extending from behind the arch portion T to the Achilles tendon portion A above the heel portion 10. Accordingly, the sock can be formed in a state such that it hangs at the position of the Achilles tendon, so as to prevent the sock from slipping while walking. Reference Numerals 4 and 5 are gore lines formed on the toe portion.

FIG. 2 is a drawing illustrating the sock S of this example viewed from above. The sock S has the heel portion 10, the size control course 9, and the additional pocket 8, formed continuously to fit the shape of the heel, and also to cover the entire body of the heel. Additionally, as shown in FIG. 2, the upper part of the compression area 7 is positioned between the elastic welt 1, the heel portion 10, the size control course 9, and the additional pocket 8, which are formed continuously.

Next, the process for knitting this sock is described in detail. FIG. 3 is a drawing illustrating the order of knitting, indicated by an arrow. FIG. 4 is a development diagram of the sock.

The process for producing sock S of this example employs a 140-needle K-type (single-cylinder) pile knitting machine, which is a type of circular knitting machine. First, as shown in FIG. 4, the elastic welt 1 is knit with normal knitting having 17 courses using all needles with normal rotation of the circular knitting machine cylinder, and then the ankle portion is knit with 4 courses.

Then, the instep side 3 of the toe portion is knit with the desired course knitting by reverse knitting through repeatedly alternating normal rotation and reverse rotation of the circular knitting machine cylinder and decreasing the number of stitches, and then performing a desired course knitting of the sole side 6 of the toe portion by reverse knitting and increasing the number of stitches. In this Specification, “increasing the number of stitches” and “decreasing the number of stitches” refer to states in which by comparing the number of stitches at the initial position of the knitted portion and the number of stitches at the final position, when the number of stitches is greater, it is considered to be “increasing the number stitches,” and when the number of stitches is reduced, it is considered to be “decreasing the number of stitches.” Therefore, this also includes the case where the needles are minutely raised and lowered at a position in the center of the knitted portion.

The following is a description of a specific case of the sock S of this example. As shown in FIG. 4, the instep side 3 of the toe portion is knit with 10 courses by half rotation knitting, raising the needles one at a time for each course, and then shifting two rows up and knitting 25 courses. Then, 16 courses are knit, raising and lowering a single needle for each course again, to form a knitted fabric along the bulge in the vicinity of the toes of the toe portion.

As shown in FIG. 4, the procedure for knitting the instep side 3 of the toe portion involves “decreasing the number of stitches” if the initial and final number of stitches are compared, even though it includes a portion in the center in which the needles are raised and lowered. The sole side 6 of the toe portion is knit by reversing the above procedure. The procedure for knitting the sole side 6 of the toe portion involves raising and lowering the needles in the center, but if the initial and final number of stitches are compared, this procedure results in “increasing the number of stitches.” In this example, minutely raising and lowering the needles at the center results in a knitted fabric formed along a bulge in the vicinity of the toes of the toe portion, thereby enhancing the wearer's feeling of a good fit.

After knitting the toe portions 3 and 6, the compression area 7 is knitted with a desired course knitting by normal knitting. In the process for producing the sock of the present invention, the toe portions 3 and 6 are knit in the manner described above, thereby making it possible for the compression area 7 to then be formed laterally in a diagonal direction from behind the arch portion T to the Achilles tendon portion A above the heel portion 10. At this stage in the process of producing this example, rubber yarns made of polyurethane coated with polyester yarns are inlaid, while interknitting the ground yarns. In addition, the compression area 7 is knit with 14 courses by normal knitting, as shown in FIG. 4.

After knitting the compression area 7, the additional pocket 8 is knit with 6 courses using reverse knitting, and the size control course is knit with 8 courses by normal knitting. Moreover, as shown in FIG, 4, the heel portion 10 is knit with 16 courses by reverse knitting, with a half needle on the opposite side from the half needle of the cylinder used when knitting the additional pocket 8. Accordingly, as shown by the arrow in FIG. 3, a part 11 (a Rosso linking course) where an opening is sewn once knitting is completed, is formed at a position on the sole side of the heel portion 10.

Therefore, in the sock produced using the process for the production of the sock of the present invention, the Rosso linking course 11 is formed at a position on the heel where the skin is thickest on the bottom of the human foot, so that even with the presence of the Rosso linking course 11, there is no feeling of discomfort while wearing the sock.

The following is an explanation of the methods and results of tests performed to verify the advantageous effects of the sock of the present invention. In these tests, the example of a sock of the present invention shown in FIG. 1 is referred to as “Example 1.” Two prior art samples of socks with a structure having nothing corresponding to the compression area of the present invention, although an elastic welt is provided in the opening welt, are referred to as “Comparative Example 1” and “Comparative Example 2.” Four tests were performed to verify the advantageous effects: A sock stretching test (elasticity); a sock stretching test (tensile force); a slipping measurement test; and a wearing test. The test methods and results are described below.

1) Sock Stretching Test (Elasticity)

A sock of Example 1 was compared with socks of Comparative Examples 1 and 2, to determine to what extent there was a difference in elasticity between the heel and the arch when the sock is worn. The distance between the heel and the arch was measured when the sock was not worn, and the distance between the heel and the arch was measured when the sock was worn, and the ratio between the two was obtained. In order to measure this distance when the sock was worn, a test piece was caused to be worn on a standard female foot mannequin.

Test Method:

-   -   1. A straight line was drawn with a marker from the heel portion         of the sock to the center of the arch portion.     -   2. The length was measured with a measuring tape.     -   3. The sock was caused to be worn on a standard female foot         mannequin, and a measuring tape was used to measure the distance         along the line made by the marker.     -   4. The elasticity was determined, setting the distance in the         unworn sock at 100%.

TABLE 1 Comparative Comparative Test Sock Example 1 Example 2 Example 1 Elasticity (%) 137 132 150

As shown in TABLE 1, the sock of the example of the present invention was found to have higher elasticity than the socks of Comparative Examples 1 and 2. The fact that the elasticity is high between the heel and the arch means that holding power is high between the heel and the arch. Therefore, even in ankle-length socks, slipping of the elastic welt can be prevented without the compression of the elastic welt being excessively high.

2) Sock Stretching Test (Tensile Force)

A sock of Example 1 was compared with the socks of Comparative Examples 1 and 2, to determine to what extent there was a difference in tensile force between the heel and the arch when the sock is worn.

Test Method:

-   -   1. A sock sample was measured as the product as such without         cutting off any part (clamping length: 1 cm).     -   2. The direction of pull was in the direction of the length from         behind the arch to the Achilles tendon portion.     -   3. While the tip of a marker of the compression area from behind         the arch portion to the Achilles tendon portion was fixed, the         tensile force of the samples was measured 3 times, and an         average value was obtained.     -   Tester: AUTOGRAPH AGS-H (SHIMADZU)     -   Test conditions: 19.9° C., 64%, pulling speed of 300 mm/min

TABLE 2 Comparative Comparative Test Sock Example 1 Example 2 Example 1 Tensile force (N) 2.7 2.7 5.0

As shown in TABLE 2, in the sock of Example 1, the tensile force of the compression area is 5.0 (N), exhibiting a higher tensile force than in Comparative Examples 1 and 2, both of which have a tensile force of 2.7 (N). Since the sock of the present invention exhibits a higher tensile force between the heel and the arch than the sock of the prior art, slipping of the elastic welt is prevented, even in an ankle-length sock.

The present inventors have determined that in the present invention, a slip-preventing effect can be achieved suitably, and that it is preferable that the tensile force of the compression area 7 is ±0.5 N of the value for 5.0 N of Example 1 (i.e., 4.5-5.5 N), according to various investigations under conditions where there was no loss of comfort of the sock.

3) Slipping Measurement Test

A sock of Example 1 was compared with the socks of Comparative Examples 1 and 2, to determine whether or not there actually was a slip-prevention effect. This test was performed by causing a sock of Example 1 to be worn on a standard female foot mannequin, and measuring the stress when pulled in various directions.

Test Method:

-   -   1. The holding clipper of a digital force gauge was attached at         the desired position on each of the samples, and the tensile         force was measured at the point in time when the slipping         phenomenon occurred, and the ease with which the sock came off         was compared to when it was pulled in the horizontal direction.     -   2. Each sample was measured 20 times, and an average value was         obtained.     -   Measuring device: Digital force gauge (Imada, Inc., ZP50N)     -   Test conditions: Tested sock was worn on a model of a foot         (model of average HQL 20-year-old Japanese female foot)

The four positions where the holding clipper was attached were prepared as below. (See FIGS. 8-11). In FIGS. 8-11, Reference Numerals 81, 91, 101, and 111 represent the measuring device (digital force gauge), and Reference Numerals 82, 92, 102, and 112 represent the pulling direction.

-   -   Heel side of the elastic welt: The position of Reference Numeral         83 in FIG. 8     -   Center of the arch portion: The position of Reference Numeral 93         in FIG. 9     -   Outer side of the sole portion near the heel (foot mannequin set         at −45°): The position of Reference Numeral 103 in FIG. 10.     -   Inner side of the sole portion near the heel (foot mannequin set         at +45°): The position of Reference Numeral 113 in FIG. 11.

TABLE 3 (Unit: N) Comparative Comparative Test Sock Example 1 Example 2 Example 1 Heel side of elastic welt 1.60 ± 0.13 1.05 ± 0.11  5.50 ± 0.49 Center of arch portion 7.42 ± 0.61 3.15 ± 0.32 11.99 ± 1.22 Outer side of the sole portion 7.89 ± 0.92 2.73 ± 0.15 21.72 ± 2.13 near the heel Inner side of the sole portion 8.26 ± 0.40 3.65 ± 0.27 23.77 ± 2.84 near the heel

The tensile force occurring when the phenomenon of slipping occurred in the sock of Example 1 was compared with that of Comparative Examples 1 and 2. The tensile force was found to be 3.4-5.2 fold at the heel side of the elastic welt; 1.6-3.8 fold at the center of the arch portion; 2.7-7.9 fold at the outer side of the sole portion near the heel; and 2.8-6.5 fold at the inner side of the sole portion near the heel. Therefore, the tensile force of Example 1 was found to be higher at all positions. This directly confirmed that if the structure of the present invention is employed, slipping of the elastic welt can be prevented, even in an ankle-length sock.

4) Wearing Test

A wearing test was performed to determine whether or not the sock of the present invention has the effect of preventing slipping and retracting when wearing and taking off a shoe.

Test Method:

-   -   1. The sock of Example 1 was worn by 3 test subjects with sock         wearing detection monitors. (Foot lengths—Monitor A: 22.8 cm;         Monitor B: 22.6 cm; Monitor C: 22.1 cm)     -   2. Athletic shoes were worn with the socks (size of athletic         shoes: 23.0 cm).     -   3. Test subjects were asked to remove the shoes after putting         them on.

TABLE 4 Comparative Comparative Test Sock Example 1 Example 2 Example 1 Monitor A Slipped off Slipped off Did not slip off Monitor B Slipped off Slipped off Did not slip off Monitor C Did not slip off Did not slip off Did not slip off

The sock slipped off when worn by test subjects in the case of Monitor A, Monitor B, Comparative Example 1, and Comparative Example 2, but the sock of Example 1 did not slip off when worn by any of the 3 test subjects with sock wearing detection monitors. These results confirm that the knitting structure of the sock of the present invention is such that the elastic welt does not slip and retract into the shoe as readily as in the sock of the prior art. 

1. A sock having an ankle length with an opening welt positioned in the vicinity of an ankle of a wearer, and having an elastic welt provided at the opening welt, the sock comprising: a compression area with high elasticity and high compressive force disposed laterally in a diagonal direction in an area extending from behind an arch portion to an Achilles tendon portion above a heel portion.
 2. A sock according to claim 1, further comprising a size control course with a knitted fabric increased by 4-20 courses disposed between the compression area and the heel portion.
 3. A sock according to claim 2, further comprising an additional pocket interknitted with 2-24 courses by reverse knitting, repeatedly alternating normal rotation and reverse rotation of the circular knitting machine cylinder, at a position on the sole portion side between the size control course and the compression area.
 4. A sock according to claim 1, wherein the tensile retention force of the compression area is between about 4.5 Newtons to about 5.5 Newtons.
 5. A process for producing a sock using a circular knitting machine, the process comprising: course knitting an elastic welt and an ankle portion using normal knitting with normal rotation of a circular knitting machine cylinder; course knitting the instep side of the toe portion by reverse knitting, repeatedly alternating normal rotation and reverse rotation of the circular knitting machine cylinder, and decreasing a number of stitches; course knitting a sole side of the toe portion by reverse knitting and increasing the number of stitches; and inlaying elastic yarns while knitting ground yarns when course knitting the compression area by normal knitting.
 6. The process according to claim 5, further comprising: course knitting the compression area; knitting the additional pocket with 2-24 courses by reverse knitting; knitting the size control course with 4-20 courses by normal knitting; knitting a heel portion by reverse knitting with a half needle on the opposite side from the half needle of the cylinder used when knitting the additional pocket; and seaming the opening upon completion of knitting, so that the seamed opening is positioned on the sole side of the heel portion. 